Devices for immersion into a bath of molten ferrous metal to retrieve a sample and methods of using the same are known. A typical device includes an expendable probe having a chamber which is adapted to be filled with the molten metal after a protective layer over an inlet to the chamber is consumed by the bath. In the chamber it is necessary to provide a deoxidant. The amount of deoxidant varies from manufacturer to manufacturer over the range of about 0.2-1% by weight of the sample and steel grades.
Most steel manufacturers use two such devices per heat. Some steel manufacturers take a first sample in an oxygen furnance during in-blow, namely when oxygen is being blown into the molten metal. Other manufacturers take the first sample during a time known as blow-interrupt, that is, after blowing of oxygen has ceased. The second sample is taken at the end of the heat to verify predicted results. Testing of commerically available sampling devices at each of said time periods shows erratic results with respect to quality of samples and/or the quality of carbon readings.
Quality of samples refers to the lack of pin holes or other undesirable features. Carbon readings are reflected by a cooling curve which is monitored by a computer correlated with a desired cooling curve. Poor quality carbon readings are those which deviate from the desired cooling curve by more than 1.5.degree. C.
The present invention is directed to a solution of a problem of how to sample molten metal and obtain a reliable carbon reading and good samples.